The silky pyramid bag looks like the posh option. You can see whole-looking leaves through the mesh, it costs more than the paper kind, and it sits in your mug like a little piece of luxury.
That mesh is usually plastic. Steep one and it sheds billions of particles into a single cup, and the plain paper bag next to it is often less paper than it looks. Even the oldest insult about tea bags, that they're full of floor sweepings, turns out to be wrong, and the truth flatters the bag. And half the story has nothing to do with the bag at all. It comes from the tea plant itself.
What's inside the bag
The tea bag started life as cloth. The first patent was filed in 1901 by two women from Milwaukee, Roberta Lawson and Mary McLaren, for a sewn fabric "tea leaf holder". The better-known story credits a New York merchant, Thomas Sullivan, who sent tea samples out in little silk pouches, and the legend goes that his customers dropped the whole pouch into the pot.
As for what's inside, the floor-sweepings line is a good insult and a bad description. When tea is processed, the leaves break into pieces of every size. The big pieces are sold as loose leaf, and the smallest grades, called fannings and dust, go into bags. They're real tea, just broken small.
That's the whole point of a bag. Small pieces give up their colour, caffeine and flavour fast, so a bag makes a strong cup in a couple of minutes. It also means the bag is rarely the weaker tea. When bagged and loose green tea were brewed side by side, the bagged one put more of tea's best-known antioxidant into the cup. Broken leaf gives everything up at once.
So the case against tea bags has little to do with what's in the tea. It's about what the tea comes wrapped in, and what the plant brings with it.
The plastic in the bag
Tea bags come in three kinds of material, and two of them contain plastic.
Silky mesh bags, usually pyramids, are made of nylon or PET, the plastic used for drinks bottles. The pyramid shape only arrived in the late 1990s, sold as giving the leaves room to move, which makes the plastic the newest thing in your mug. When a single one was steeped at brewing temperature, it released around 11.6 billion microplastic particles and 3.1 billion even smaller nanoplastic particles into the cup, a load far higher than anything previously measured in other foods.
The exact count has been argued over, since some of what looked like plastic turned out to be tea residue clinging to the mesh. The direction is clear, though. Heat a plastic mesh in hot water and it sheds, and putting the mug in the microwave makes it shed more.
Paper bags are mostly plant fibre, and some have polypropylene fibres mixed in so the edges can be heat-sealed shut. A gardener in Wales noticed it in 2017, when his composted tea bags left a plastic residue behind in the soil. Some big brands have since changed their bags, others still use the plastic, and the box rarely says which.
"Plant-based" bags are made from PLA, a plastic produced from corn starch. It sounds reassuring, and it's still plastic. When different tea bags were buried in soil for a year, the plain paper ones disappeared within months, the paper-and-plastic blends crumbled into fragments that were still there a year later, and the bags made purely of PLA, sold as completely biodegradable, came out intact.
Where the plastic goes
Plastic particles small enough to come out of a tea bag are small enough to get into the body. When nanoplastics from ordinary tea bags were put on human gut cells in a dish, the cells took them up within a day.
What happens next is the part that should make you put the kettle on more thoughtfully. When people having fatty plaque removed from the arteries in their neck were followed for nearly three years, those whose plaque contained microplastics were about four and a half times more likely to have a heart attack, a stroke or die than those whose plaque was clean. More than half of them had plastic in their arteries. It shows a link, and the plastic in those arteries came from food, water, air and packaging over a lifetime. A tea bag is one of the few sources you can remove for good, by changing one habit.
What the plant brings with it
Now for the half that has nothing to do with the bag. The tea plant pulls fluoride out of the soil and stores it in its leaves, more than almost any other food plant. The older and tougher the leaf, the more fluoride it holds, and the longer you brew it, the more comes out into the cup. In one check of everyday supermarket teas, nearly every cup carried more fluoride than tap water that has fluoride added on purpose.
That matters for bags, because when shop-bought teas were compared in two European countries, the bagged teas carried more fluoride than loose leaf, and in one of them more aluminium too. The tea plant collects both. Black tea carries more than green, and white tea, made from young buds, carries the least. The grade matters more than the packaging, though: cheap loose tea made from older leaves can carry just as much as a bag.
Matcha deserves its own line. It's the leaf itself, ground to powder and whisked into the water, so everything the leaf holds goes down with it. In that supermarket check, matcha carried the most fluoride of all.
For an adult, a few cups a day add a modest amount of fluoride. The trouble comes with heavy drinking, especially where the tap water is fluoridated too. Ireland shows how it adds up: it's among the heaviest tea-drinking countries in the world, it fluoridates its tap water, and every one of 54 bagged black teas sold there released fluoride into the cup, the strongest nearly four times as much as the weakest.
Children are a different matter. They take in more fluoride for their size, so keep a young child's tea weak and occasional, or make it herbal.
A woman in her forties was sent for tests with bone pain and odd-looking X-rays, and the cause turned out to be tea. For seventeen years she had drunk a pitcher a day brewed from 100 to 150 tea bags. The diagnosis was skeletal fluorosis, where fluoride builds up in the bones and makes them dense, stiff and painful. It's an extreme case, and it shows where fluoride ends up when the body takes in too much. Weak kidneys clear fluoride poorly, so heavy tea drinkers with kidney disease are the most exposed.
Lead turns up too. When 30 ordinary bagged teas were checked, every brewed cup contained some lead, and a long steep pulled out more than a short one. Aluminium came out above guideline levels in a fifth of them. The plant takes up what's in the soil, and the cup takes up what's in the plant.
If tea is your all-day drink, herbal blends make good stand-ins for some of the cups. They carry only a small fraction of black tea's fluoride, and the same bag rules apply to them. is an easy first pick: caffeine-free, with a rich, slightly sweet taste.
Why loose leaf wins anyway
Loose leaf solves both problems at once. No bag means no plastic in the cup, and a good loose tea keeps the fluoride down too. You can see exactly what you're brewing, and if a tea is mostly dust, it shows.
Whole leaves also brew more than once. A good oolong or green tea can give two, three or more cups from the same leaves, with the flavour changing as the leaf opens. That changes the maths. A decent loose tea that costs more per gram than a supermarket box can end up cheaper per cup, because each spoonful is used two or three times.
And it tastes better. Whole leaves release their flavour slowly, so the cup comes out rounder and forgives you for leaving it a minute too long.
How to switch without the faff
The kit is small. A steel mesh basket that sits in your mug, wide enough for the leaves to open, does the same job as a bag, and a with two handles rests on the rim of most mugs. For a pot, a keeps everything that touches the tea in glass. A spoonful of leaves per mug is the place to start, adjusted to taste.
Water temperature matters more with loose leaf. Black tea likes water straight off the boil. Green and white teas turn bitter in boiling water, so let the kettle sit for a few minutes before pouring. Keep brewing times short, which also keeps the fluoride down, and steep the same leaves again for the next cup.
Keep plastic out of the kit too. Brewing loose leaf in a plastic infuser or a plastic tea bottle brings the problem straight back: polypropylene bottles filled with hot water released up to 16 million particles per litre, and hotter water released more. Steel, glass or ceramic for anything that touches the hot water.
The kettle and the cup matter as much. Plastic kettles shed microplastics into hot water, and a layer of limescale inside the kettle cut that release by more than 89 per cent, so descaling a plastic kettle strips away the layer that was holding the plastic back. A steel or glass kettle avoids the question, and an all-steel electric kettle with temperature control also gives green tea the cooler water it needs. Takeaway paper cups are lined with a thin plastic film that sheds into hot drinks, which makes your own cup the better habit.
Store the tea in an airtight tin, away from light and strong smells, because leaves soak up odours from the cupboard.
If you keep using bags
Bags have their place, at work, travelling or when you just want a quick cup. Choose ones sold as plastic-free, and skip the silky mesh pyramids. Leave the microwave out of it, and heat the water first.
When the box gives nothing away, the bag will. See-through silky mesh is plastic. A paper bag with edges pressed and fused shut usually has plastic fibres in it, because heat-sealing needs something that melts. Bags that are folded, stitched or tied with cotton string get by without it.
Keep the tea, mind the caffeine
None of this is a reason to give up tea. Across nearly half a million adults in Britain, those who drank two or more cups a day were around 12 per cent less likely to die over the following eleven years than those who drank none, and the pattern held for heart disease and stroke. The tea in question was mostly black, the same kind that usually comes in bags.
And tea counts as fluid. When men drank four or six mugs of ordinary black tea through the day, they stayed as well hydrated as on the same amount of water, caffeine and all.
Two cautions belong with it. The smaller one is iron: tea binds iron from plant foods and makes it harder to absorb, so if your iron runs low, drink it between meals.
The bigger one is caffeine. A cup of black tea carries roughly half the caffeine of a cup of coffee, and the broken leaf in a bag releases it fast. Caffeine also lingers: the body clears about half of it in five hours or so, and the caffeine of several strong coffees taken six hours before bed still cut sleep by more than an hour. If your nights are short, make the later cups herbal.
If you're pregnant or trying to conceive, keep caffeine out altogether, from tea, coffee, cocoa, cola and energy drinks alike. It crosses the placenta freely, and the baby's blood ends up with much the same level as yours. Children feel it more for their size too, which gives their tea a second reason to stay weak or herbal.
Change the box, keep the ritual
The silky pyramid was never the luxury option. It's broken tea in a plastic net, and the paper bag beside it may be holding plastic fibres of its own. The leaf inside is innocent by comparison. It does bring fluoride and lead up from the soil, and a short brew of a good leaf keeps both low.
So when the next box runs out, replace it with a pack of loose leaf and a steel basket. Brew it short, steep it twice, and make the last cup of the day herbal. The tea was always the good part, and now the rest of the cup can match it.
Wondering where else plastic gets into your food? Hidden Food Contamination: BPA, Microplastics, and Heavy Metals in Your Clean Diet — the foods sold as clean that carry plastic and metals, and the swaps that cut the load.
Looking for something else to drink through the day? What to Drink Instead of Plain Water — and What the Popular Alternatives Do to Your Body — which drinks hydrate you, and which work against you.
Know someone who buys the silky pyramid tea bags because they look like the good stuff? Send them this. Their next box could be the plastic-free kind.
Disclaimer: This article is general information. For advice about your own health, talk to a qualified health professional. If you're pregnant or trying to conceive, keep caffeine out altogether.
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